The Water Environment Bearing Capacity Assessment Index System and Model were constructed respectively from DPSIRM and SVR Model, then parameters of the SVR Model were optimized via cross-validation methodology to further improve the accuracy of the prediction. The evolution trend and spatial differences of water environment carrying capacity of Yangtze River Economic Zone from 2009~2018 were studied using the Model. Water Environment Bearing Capacity Grade of Yangtze River Economic Belt presents an upward trend in a whole, the bearing level of the city agglomeration of upstream and midstream of the River has been improved from level II (overload) to level IV (weakly loadable), while the level of the downstream area changed from Level I (heavy overload) to Level IV (weakly loadable). By comparing the evaluation results of the Model and entropy weight-TOPSIS method, the coincidence rate reaches 91.7%, the SVR model is feasible to evaluate the water environment carrying capacity and the results are reliable. The bearing capacity of six subsystems of the downstream region was analyzed, then the sensitivity analysis on evaluation indicators in each subsystem was performed based on Single Factor Alternate Method (OAT) so as to help decision makers identify the sensitivity of indicators.